1. Field of the Invention:
The present invention relates to a cooking apparatus with a weighing device which is capable of measuring the weight of an object to be heated and automatically controlling the output of a heating source, the heating mode, the heating time and so forth in accordance with the measured weight.
2. Description of the Prior Art:
To carry out cooking by means of conventional cooking apparatus such as a high-frequency heater, it is generally necessary to conduct complicated and troublesome operations such as those described in the following and, therefore, it has not been easy to handle such conventional cooking apparatus. Two examples of prior cooking apparatus will be explained hereinunder.
Referring first to FIG. 1 which shows the structure of one example of prior cooking apparatus, a heating chamber 1 has a door 2 provided on its front side in such a manner that it is possible for the door 2 to be opened and closed as desired. The heating chamber 1 is connected with a waveguide 3 which is provided at the other end thereof with a magnetron 4 serving as a heating source. The radio wave oscillated from the magnetron 4 is applied to the inside of the heating chamber 1 through the waveguide 3. A food 5 is mounted on a rotary plate 6 which is rotated by a motor 7 during heating for the purpose of effecting uniform heating, whereby the food 5 is subjected to high-frequency heating. Such a prior cooking apparatus, however, involves a troublesome operation in which it is necessary for the user to set a heating time in accordance with the amount or weight of each individual food 5 to be heated by means, for example, of a time switch.
Referring next to FIG. 2 which is a fragmentary sectional view of another example of prior cooking apparatus, a food 8 is placed on a rotary plate 9 which is in turn mounted on a rotary table 10. The rotary table 10 is supported by a shaft 11 which is retained by a bearing 12 and a bearing 13 in; such a manner that the shaft 11 is rotatable and movable in the direction of thrust. The shaft 11 is provided with a gear 14 which is engaged with a gear 16 which is provided on a motor 15, whereby the shaft 11 is rotatingly driven by the motor 15 through the gears 14 and 16. The shaft 11 is further supported by a support plate 18 which is in turn supported by a spring 17 such that the load downwardly applied to the shaft 11 is borne by the support plate 18. Thus, when the food 8 is placed on the rotary plate 9, the support plate 18 moves to a position where the weight of the food 8 is canceled by virtue of the resiliency of the spring 17 which is compressed to a degree corresponding to the weight of the food 8. The respective positions of the rotary table 10 and the support plate 18 in the state wherein no food 8 is placed on the rotary plate 9 are shown by the solid line in FIG. 2, while their respective positions in the state wherein the load of the food 8 is applied to the rotary table 10 and the support plate 18 are shown by the two dot-dash chain lines.
In consequence, it is possible to measure the weight of the food 8 by detecting the movement or position of the support plate 18. If the operation of the magnetron is controlled by employing an output obtained as the result of such detection, it is conveniently possible to effect an appropriate heating operation in accordance with the amount or weight of the food 8 without any need to set a heating time for each individual food 8.
Such a prior cooking apparatus, however, suffers the following disadvantages. Namely, the engagement between the gear 14 provided on the shaft 11 and the gear 16 unfavorably involves resistance to the vertical movement of the shaft 11. Further, since a frictional resistance occurs between the shaft 11 and the bearings 12 and 13, it is not easy for the load of the food 8 to be accurately transmitted to the support plate 18. For this reason, it is not possible to effect accurate measurement of weight of the food 8, which fact disadvantageously leads to setting of an incorrect heating time and consequently involves incapability of effecting an excellent heating operation.
Further, the rotary plate 9 and the rotary table 10 in a non-loaded state are raised to their respective positions shown by the solid line and, there is therefore a difference in level between the rotary plate 9 and the bottom surface of the heating chamber relative to the upper surface of the door when it is open. For this reason, when the door is opened and the rotary plate 9 is taken out of the heating chamber, it is not easy to pull out the rotary plate 9. Furthermore, since the rotary table 10 is supported by the spring 17, when the rotary plate 9 or the food 8 is mounted thereon, the rotary table 10 is vertically moved and therefore unstable. Thus, this type of prior cooking apparatus is inconvenient for use and may make the user feel uncomfortable when operating the apparatus.